Downing Street said that everyone who served in a Cabinet post under Lady Thatcher had been invited.

Lord Heseltine, whose leadership challenge in 1990 helped end Lady Thatcher’s premiership, confirmed that he would attend Wednesday’s ceremony with his wife.

Lord Howe, whose resignation as Lady Thatcher’s deputy prime minister hastened her fall, has also been invited to the service.

Neither man spoke in the House of Lords debate to pay tribute to Lady Thatcher this week. Lord Howe was present in the chamber and appeared to have prepared a speech, but did not speak. Sir John Major, Lady Thatcher’s successor as prime minister, will attend. Whitehall sources said that the precise attendance of Lady Thatcher’s former colleagues was still uncertain because of their varied age and state of health.

One of the oldest guests is expected to be Sir Clive Bossom, 95, a former Conservative MP who served as an aide to Lady Thatcher when she was a junior minister in the Macmillan government in the 1960s.

Lord Carrington, 93, who resigned as foreign secretary over the Argentine invasion of the Falklands, has been invited.

Lord Archer of Weston-super-Mare, the former Conservative deputy chairman once jailed for perjury, is also expected to attend. Lord Kinnock, who was defeated by Lady Thatcher in the 1987 general election, criticised her record in office this week and accused her of leaving Britain a poorer and more unequal place.

Sources said that despite their political differences, Lady Thatcher would have wanted him to be invited to her funeral.

However, the former Labour leader pre-empted any invitation by making clear that he would not attend the ceremony, citing a prior commitment.

“He will not be attending because a councillor in his old constituency died a few days before Lady Thatcher,” a spokesman said. “He promised he would get to the funeral. He will be in Wales.”

It is understood that the funeral is that of Olga Griffiths, a former councillor in Lord Kinnock’s old Islwyn constituency. She died on March 29.

One Labour source said that even without that commitment, Lord Kinnock might not have attended Lady Thatcher’s funeral. “He would have stayed away because he wouldn’t want to be a hypocrite,” the source said.

Lord Kinnock will not be attending the funeral

Later Labour leaders including Tony Blair and Gordon Brown will attend the funeral. Also invited is Michael Portillo, the former Conservative Cabinet minister who was once regarded as a potential political heir to Lady Thatcher.

Baroness Boothroyd, the former Commons Speaker, is also thought to have been invited.